Single crystals of K2B4O11H8, a non-centrosymmetric borate material, have been prepared by slow evaporation of water solution at room temperature. The crystals were colorless and transparent with smooth faces. The single-crystal X-ray diffraction analysis showed that K2B4O11H8 crystallized in the orthorhombic space group P212121 with a=6.8556(6) A˚, b=11.7787(12) A˚, c=12.8949(14) A˚, Z=4, R1=0.0188, and wR2=0.0464. The powder X-ray diffractometry (PXRD), infrared spectrum, transmittance spectrum, TG-DTA curves and second harmonic generation properties of title compound have been determined.